7 search hits

We study the line shapes of radiative $\phi$-decays with a direct coupling of the $\phi$ meson to the $f_{0}(980)$ and $a_{0}(980)$ scalar mesons. The latter couple via derivative interactions to $\pi_0 \pi_0$ and $\pi_0 \eta$, respectively. Although the kaon-loop mechanism is usually regarded as the dominant mechanism in radiative $\phi$ decays, here we test a different possibility: we set the kaon-loop to zero and we fit the theoretical curves to the data by retaining only the direct coupling. Remarkably, satisfactory fits can be achieved, mainly due to the effects of derivative interactions of scalar with pseudoscalar mesons.

A three flavor linear sigma model with vector and axial-vector mesons is discussed. Preliminary results concerning on the symmetry breaking pattern, the question of parameterization, as well as the resulting meson masses are presented.

In this proceeding the emergence of a composite, adjoint-scalar field as an average over (trivial holonomy) calorons and anti-calorons is reviewed. This composite field acts as a background field to the dynamics of perturbative gluons, to which it is coupled via an effective, gauge invariant Lagrangian valid for temperatures above the deconfinement phase transition. Moreover a Higgs mechanism is induced by the composite field: two gluons acquire a quasi-particle thermal mass. On the phenomenological side the composite field acts as a bag pressure which shows a linear dependence on the temperature. As a result the linear rise with temperature of the trace anomaly is obtained and is compared to recent lattice studies.

We discuss deviations from the exponential decay law which occur when going beyond the Breit-
Wigner distribution for an unstable state. In particular, we concentrate on an oscillating behavior,
remisiscent of the Rabi-oscillations, in the short-time region. We propose that these oscillations
can explain the socalled GSI anomaly, which measured superimposed oscillations on top of the
exponential law for hydrogen-like nuclides decaying via electron-capture. Moreover, we discuss
the possibility that the deviations from the Breit-Wigner in the case of the GSI anomaly are (predominantely)
caused by the interaction of the unstable state with the measurement apparatus.
The consequences of this scenario, such as the non-observation of oscillations in an analogous
experiment perfromed at Berkley, are investigated.

In the framework of an interference setup in which only two outcomes are possible (such as in the case of a Mach–Zehnder interferometer), we discuss in a simple and pedagogical way the difference between a standard, unitary quantum mechanical evolution and the existence of a real collapse of the wavefunction. This is a central and not-yet resolved question of quantum mechanics and indeed of quantum field theory as well. Moreover, we also present the Elitzur–Vaidman bomb, the delayed choice experiment, and the effect of decoherence. In the end, we propose two simple experiments to visualize decoherence and to test the role of an entangled particle.

We enlarge the so-called extended linear Sigma model (eLSM) by including the charm quark according to the global U(4)r × U(4)l chiral symmetry. In the eLSM, besides scalar and pseudoscalar mesons, also vector and axial-vector mesons are present. Almost all the parameters of the model were fixed in a previous study of mesons below 2 GeV. In the extension to the four-flavor case, only three additional parameters (all of them related to the bare mass of the charm quark) appear.We compute the (OZI dominant) strong decays of open charmed mesons. The results are compatible with the experimental data, although the theoretical uncertainties are still large.